Torque-controlling shafts equipped with cross bores and grooves are used both in continuously variable automatic transmissions and in multi-stage automatic transmissions to supply hydraulic fluid to individual components of the transmission, such as torque converters and shifting components, wherein the cross bores are ordinarily designed as cylindrical bores having a transfer radius at the outlet point.
One example of this type of multi-stage automatic transmission is described by the applicant in DE 199 08 840. In this case, the multi-stage automatic transmission is equipped with a number of clutches and brakes. A torque-controlling sleeve shaft feeds coolant to a clutch, discharging it through the radial cross bores in the torque-controlling shaft. The torque-controlling shaft is also equipped with grooves for various gaskets.
An example of a continuously variable automatic transmission having a multi-plate clutch is described by the applicant in DE 197 34 839 A1. In this case as well, a primary shaft, designed as a torque-controlling shaft, is provided with cross bores for the introduction of fluid for lubrication and cooling of a multi-plate clutch; these cross bores are ordinarily designed as cylindrical cross bores having a transfer radius at their outlet point. This primary shaft is also equipped with grooves for gaskets. It has been found that torque-controlling shafts of this type having cross bores and grooves, used in automatic transmissions, especially in vehicles, are susceptible to fracture under certain conditions due to a notch effect. Fractures tend to begin in the outlet area of the cross bores and grooves. Increasing the strength of these torque-controlling shafts having cross bores by improving the materials used to manufacture them, or by optimizing the tempering process, is not economically feasible due to the increased costs. Attempts have also been made to vary the positioning, the number, and the diameter of the cross bores, and to reduce the notch effect by improving surface quality. In such cases, the function of the flow of oil required for the optimal operation of the automatic transmission is often unacceptably restricted. In order to produce the necessary strength levels, the torque-controlling shafts must be strengthened in the area of the cross bores and grooves. For reasons of vibration technology, it is necessary for the torque-controlling shafts to have low torsional stiffness. But increasing strength around the cross bores and grooves substantially increases torsional stiffness. In addition, the overall diameter, and thus also the overall size of the component, are negatively affected. Furthermore, known-in-the-art torque-controlling shafts are comprised of many components, which require costly sealing methods. The main components of these torque-controlling shafts are the turbine shaft, the stator sleeve shaft, and the flange.
The object of the present invention is to disclose torque-controlling shafts that can be used in the central supply of fluid to a torque converter and to shifting elements in an automatic transmission, in which cross bores and grooves, and the related, required increases in strength, can be eliminated, thus preventing increases in torsional stiffness, and reducing the number of components required, the size of the unit, and leakage.
The object of the invention is attained with an automatic transmission of the type described, having the characterizing features of the main claim.